1. Field of the Invention
This invention relates to a signal separation apparatus and related method thereof, and more particularly, to a signal separation apparatus and related method applied in an image transmission system.
2. Description of the Prior Art
Color televisions had been invented for more than fifty years, and the composite video signal utilized by the color televisions includes a luminance signal and a chrominance signal, where a frequency of the luminance signal falls in the range from 0 Hz to 5.5 MHz and the chrominance signal is modulated on a carrier whose frequency falls in a range from 3.58 MHz to 4.43 MHz. Thus, the spectrum of the luminance signal and that of the chrominance signal overlaps while the color television receives above-mentioned composite video signal through a connector such as an AV connector. Therefore, methods for extracting the luminance signal and the chrominance signal from the composite video signal are an important issue in color television development. As is well known, separating the luminance signal Y and the chrominance signal C is commonly called Y/C separation.
Conventionally, a linear filter or a comb filer is used to perform the Y/C separation. Utilizing the linear filter to separate the luminance signal and the chrominance signal is a trivial task. However, since the spectrum of a chrominance signal overlaps the spectrum of the luminance signal, the linear filter may judge a high-frequency luminance signal as a chrominance signal erroneously. Additionally, because the high-frequency luminance signal commonly indicates the outline of an image object, utilizing a linear filter to perform Y/C separation may vague (i.e., blurred) the contour of the image object, and introduce cell contrast or stripe contrast around the outline. In order to solve the above-mentioned problems, the comb filter is used to perform the Y/C separation instead of the linear filter. However, while utilizing a comb filter to perform the Y/C separation, a related art image decoder has to determine an image corresponding to a target location in a picture as a still image, and then utilizes a 3D comb filter to perform an inter-field Y/C separation on the image located at the target location. Compared with the linear filter, the comb filter produces better Y/C separation result but its operation is more complex.